There are wireless information distribution apparatuses which perform information distribution by wireless to surrounding wireless terminals. Some of the wireless information distribution apparatuses have the function to distribute information toward only wireless terminals located within a given distance. Such wireless information distribution apparatuses are installed in, for example, movable bodies of public transportation, such as trains and buses, or facilities of public transportation, such as train platforms and bus stops, and are used to provide guidance information to only nearby passengers.
To actually distribute information to only wireless terminals located within a given distance, it is necessary to adjust a reachable distance of radio waves used for wireless communication to become constant. However, since radio waves are absorbed by persons, to make the reachable distance of radio waves constant, it is necessary to adjust a transmitted radio wave intensity corresponding to the number of persons present around the wireless information distribution apparatus.
There is a traditional technique to estimate the number of persons around an apparatus which transmits information by wireless and to increase transmitted power when the number of persons is large and decrease transmitted power when the number of persons is small (for example, see Patent Literature 1).